feat(templates): med-mal-case project template

Phase 1 of the templates → extraction-pipeline path. Selecting a template
when creating a project scaffolds the 12-folder med-mal taxonomy + nested
imaging folder, and exposes a "Recommended tabular reviews" strip on the
project page with one-click buttons for the 11 schemas validated against
Minnesota primary sources (Plutshack/Smith, § 145.682, § 548.251,
§ 144.293, Popovich, Dickhoff, Flom, Reinhardt, Cornfeldt).

Backend:
- New table column: projects.template_id (text null) - applied directly to
  prod (`qkfcrsrtualqdmqqexpf`) via Supabase MCP apply_migration after
  branch creation returned PaymentRequiredException on the free plan.
  Folded into schema.sql + backend/migrations/0001_projects_template_id.sql.
- backend/src/lib/templateIds.ts - shared string-literal unions for
  ProjectTemplateId and TabularSchemaId.
- backend/src/lib/builtinProjectTemplates.ts - registry exporting the
  med-mal-case template with its 12 subfolders and 11 recommended schema ids.
- backend/src/routes/projects.ts - POST /projects extended to parse
  optional template_id, validate against registry (400 on unknown), and
  batch-create subfolders in two passes (top-level UUIDs returned by
  Batch A resolve the array-index parent refs in Batch B). On any error
  the project row is deleted via CASCADE so the operation is atomic from
  the user's perspective.

Frontend:
- frontend/src/app/components/tabular/templateIds.ts - mirror of backend
  template/schema IDs.
- frontend/src/app/components/tabular/builtinTabularSchemas.ts - the only
  place column specs for built-in schemas live (11 schemas, ~120 columns
  total) with prompts tuned for Mayo/Epic ebook formatting. Each schema's
  description names the prima facie element or filing requirement it
  supports.
- frontend/src/app/components/projects/builtinProjectTemplates.ts -
  frontend mirror of the template registry (id, name, description,
  recommendedSchemaIds only; backend owns subfolders).
- frontend/src/app/lib/mikeApi.ts - createProject signature gains
  optional template_id arg.
- frontend/src/app/components/shared/types.ts - MikeProject gains
  template_id and subfolders fields.
- frontend/src/app/components/projects/NewProjectModal.tsx - adds a
  Template dropdown between the CM number field and the attribute pills,
  using the same Check-icon-on-select pattern as AddNewTRModal's workflow
  picker.
- frontend/src/app/components/projects/ProjectPage.tsx - on the reviews
  tab, renders a recommended-reviews strip when project.template_id is
  set. Each pill opens AddNewTRModal with the schema's title and full
  columns_config pre-populated.
- frontend/src/app/components/tabular/AddNewTRModal.tsx - accepts new
  optional initialTitle and initialColumnsConfig props that the
  recommended strip uses to seed the modal.

CLAUDE.md: documents the migrations workflow + flags the Supabase
branching limitation on the free plan so future migrations don't reach
for create_branch first.